Small
implantable electronic devices require biologically compatible
energy sources that are capable of delivering quick high-energy pulses.
Combining batteries and supercapacitors allows for high power and
energy density while providing both small size and biocompatibility.
Here, we report a hybrid supercapacitor/biobattery whereby an oxygen-reducing
cathode of bilirubin oxidase immobilized with anthracene-modified
carbon nanotubes and tetrabutylammonium bromide-modified Nafion is
coupled with a glucose bioanode of flavin adenine dinucleotide-dependent
glucose dehydrogenase. The redox polymer, dimethylferrocene-modified
linear poly­(ethylenimine), used at the bioanode simultaneously immobilizes
enzyme, mediates electron transfer, and acts as a pseudocapacitor
where capacitance of the anode scales with increased polymer loading.
Both multiwalled carbon nanotubes and carbon felt incorporated into
the anode construction improve polymer conductivity, subsequently
resulting in further improved anodic capacitance. A supercapacitor/biobattery
device of the above configuration results in a specific capacitance
of 300 ± 100 F/g, which is over 4 times higher than that of other
reported biologically derived supercapacitors.